1. Field of the Invention
The present invention relates to a digital interface, and more particularly, to a method for modifying data of a plug control register in a digital interface.
2. Discussion of the Related Art
FIGS. 1 and 2 show a conventional method for modifying data of a plug control register in a digital interface.
FIG. 1 shows connection state between audio/video nodes in a 1394 serial bus system according to the related art method.
A first audio/video node 20 includes first and second input plug control registers 21 and 22, and a first input master plug register 23. The registers 21, 22 and 23 input and output connection information between audio/video nodes connected to a 1394 serial bus 10 in accordance with a control signal of an application node(not shown). A second audio/video node 30 includes a third input plug control register 31 and a second input master plug register 32. The registers 31 and 32 input and output connection information between apparatuses connected to the 1394 serial bus 10 in accordance with the control signal of the application node. A third audio/video node 40 includes a fourth input plug control register 41 and a third input master plug register 42. The registers 41 and 42 input and output connection information connected between the apparatuses connected to the 1394 serial bus 10 in accordance with the control signal of the application node. A fourth audio/video node 50 includes fifth and sixth plug control registers 51 and 52 and a fourth input master plug register 53. The registers 51, 52 and 53 input and output connection information between the apparatuses connected to the 1394 serial bus 10 in accordance with the control signal of the application node. A fifth audio/video node 60 includes a plug control register 61 and an output master plug register 62. The registers 61 and 62 input and output connection information between the apparatuses connected to the 1394 serial bus in accordance with the control signal of the application node.
A related art method for modifying data of a plug control register of audio/video nodes will be described with reference to FIG. 2.
A channel of transmitting isochronous data from the fifth audio/video node 60 to the first audio/video node 20 by point-to-point connection or broadcast connection is assigned to an application node. The application node writes data of a plug control register and an input plug register within the fifth audio/video node 60 in the plug control register 61 and the second input plug register 22 at the same format.
Afterwards, the application node writes xe2x80x9c1xe2x80x9d in on-line bit of the plug control register 61 and on-line bit of the second input plug register 22 in the fifth audio/video node 60 to transmit the isochronous data.
Also, the application node records xe2x80x9c1xe2x80x9d in a broadcast connection counter or a point-to-point connection counter of the plug control register 61 within the fifth audio/video node 60.
Thus, the isochronous data is transmitted from the fifth audio/video node 60 to the first audio/video node 20 through the channel.
As described above, the isochronous data is transmitted from the fifth audio/video node 60 to the second and fourth audio/video nodes 30 and 40.
In this situation, the sixth audio/video node transmits a read request signal to the fifth audio/video node 60 to modify data of the plug control register 61 of the fifth audio/video node 60. Then, the fifth audio/video node 60 inputs a read response signal to the sixth audio/video node and transmits a value of its plug control register 61 to the sixth audio/video node.
The sixth audio/video node records the value of the plug control register 61 of the fifth audio/video node 60 transmitted through the read response signal in a memory as read data. The read data is an argument value.
The sixth audio/video node modifies the argument value and records the modified value in the memory as a data value.
Subsequently, the sixth audio/video node inputs a lock request signal to the fifth audio/video node and transmits the modified data value and the argument value prior to modification.
The fifth audio/video node 60 compares the transmitted argument value with a value of its plug control register 61. As a result, if the transmitted argument value is equal to the value of the plug control register 61, the fifth audio/video node 60 modifies the value of the plug control register 61 to the data value.
However, the related art method for modifying data of a plug control register in a digital interface has several problems.
In case where the sixth audio/video node is not entitled to modify the value of the plug control register of the fifth audio/video node 60 after the sixth audio/video node has received a lock transaction, the fifth audio/video node 60 cannot inform the sixth audio/video node which requested the lock transaction that the sixth audio/video node is not entitled to modify the value of the plug control register. Therefore, if the sixth audio/video node receives the lock transaction, the sixth audio/video node determines that the value of the plug control register of the fifth audio/video node has been modified whether lock transaction is entitled to modify the plug control register or not.
Accordingly, the present invention is directed to a method for modifying data of a plug control register in a digital interface that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method for modifying data of a plug control register in a digital interface in which it is recognized whether or not a value of a plug control register can be modified using a read/lock transaction between audio/video nodes connected to the digital interface.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method is provided for updating data of a plug control register in a digital interface having a plurality of audio/video nodes, the method comprising:
if a first audio/video node requests a second audio/video node to update a value of the plug control register through a read/lock transaction, retrieving a signal that determines whether the first audio/video node is entitled to update a value of the plug control register of the second audio/video node;
transmitting the determining signal to the first audio/video node through a lock response packet; and
if the first audio/video node is entitled to update the value of the plug control register of the second audio/video node and if an argument value transmitted from the first audio/video node is equal to the value of the plug control register of the second audio/video node, then updating the value of the plug control register of the second audio/video node with a data value transmitted from the first audio/video node.
According to the above-mentioned features, the present invention has the advantage that, by using a signal that determines whether or not the first audio/video node is entitled to update the value of the plug control register of the second audio/video node when the first audio/video node requests the second audio/video node to update the value of the plug control register through the read/lock transaction, it is possible to update the data of the plug control register only by the audio/video node entitled to update it.
In another aspect, the method for modifying data of a plug control digital interface includes the determining signal being at least one of a signal xe2x80x9cresp_completexe2x80x9d indicating that the first audio/video node is entitled to update the value of the plug control register of the second audio/video node and a signal xe2x80x9cresp_access_errorxe2x80x9d indicating that the first audio/video node is not entitled to update the value of the plug control register of the second audio/video node.
In still another aspect, the method for modifying data of a plug control register in a digital interface according to the present invention is characterized in that the signals xe2x80x9cresp_completexe2x80x9d and xe2x80x9cresp_access errorxe2x80x9d are recorded in xe2x80x9crcodexe2x80x9d of the lock response packet.
In another further aspect, the method for modifying data of a plug control register in a digital interface according to the present invention further includes the steps of comparing an argument value transmitted from the first audio/video node with a value of the plug control register; if the argument value is equal to the value of the plug control register, modifying a data value transmitted from the first audio/video node to the value of the plug control register using the signal as to whether to be modified as the signal xe2x80x9cresp_completexe2x80x9d; and if the argument value is equal to the value of the plug control register, maintaining the value of the specific register using the signal as to whether to be modified as the signal xe2x80x9cresp_access errorxe2x80x9d.
In another aspect, a method is provided for updating data of a plug control register in a digital interface having a plurality of audio/video nodes, the method comprising:
if a value of the plug control register of a first audio/video node is transmitted to a second audio/video node before and after the value of the plug control register of the second audio/video node is updated, retrieving a signal that determines whether the first audio/video node is entitled to update the value of the plug control register of the second audio/video node;
if the first audio/video node is entitled to update the value of the plug control register of the second audio/video node and if the value of the plug control register of the second audio/video node is equal to the value of the plug control register transmitted from the first audio/video node before the value of the plug control register of the second audio/video node is updated, then updating the value of the plug control register of the second audio/video node with the value of the plug control register transmitted from the first audio/video node after the value of the plug control register of the second audio/video node is updated; and
requesting the second audio/video node to send the updated value of the plug control register, and holding the update request from another audio/video node through a lock transaction until the first audio/video node receives the updated value from the second audio/video node.
In a still further aspect, the present invention is characterized in that lock transaction is performed at another audio/video node if the first audio/video node does not request the updated value in a predetermined time.
By holding the update request from another audio/video node through the lock transaction until the first audio/video node receives the updated value from the second audio/node, the first audio/video node can update the data of the plug control register of the second audio/video node without interruption of another audio/video node.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.